A new early peirosaurid terrestrial crocodile (Notosuchia) from La Buitrera (Candeleros Formation), Río Negro, Argentina

Abstract

Notosuchia represents one of the most morphologically diverse groups of Mesozoic crocodyliforms and was particularly abundant in the Cretaceous of Gondwana. Among them, Peirosauridae comprises medium-sized terrestrial predators widely distributed across southern continents during the Late Cretaceous. Here we describe a new peirosaurid crocodyliform, Antusuchus rionegrinus gen. et sp. nov., from the Cenomanian Candeleros Formation of the Neuquén Basin (Río Negro Province, Argentina). The material, recovered from the La Buitrera Palaeontological Area, includes cranial and postcranial remains. Micro-computed tomography and anatomical comparisons reveal a unique combination of characters, including a short rostrum, an elongated palatal depression adjacent to the maxillary tooth row, a rod-shaped jugal bar, and a prominent sagittal crest. The dentition is ziphodont and includes a hypertrophied third maxillary tooth, consistent with predatory habits. Phylogenetic analyses recover Antusuchus rionegrinus as the earliest-branching member of Peirosauridae, sister to all remaining peirosaurids. This discovery provides new insights into the early evolution of peirosaurids and highlights the importance of the La Buitrera fauna for understanding mid-Cretaceous terrestrial ecosystems and the diversification of notosuchian crocodyliforms.